Grade distribution in a porphyry copper deposit - modeling and predictive capability

Conference · Tue Jan 01 04:00:00 EST 1985 · Geol. Soc. Am., Abstr. Programs; (United States)

OSTI ID:6462449

Murdock, G; Petersen, U

Thirty-two grade profiles across the high grade dome of a porphyry copper deposit are fit by six possible element distribution functions. All six functions have a single maximum, approach or achieve a zero value away from the maximum, and are never negative. Four of the six functions are symmetric and have three parameters - symmetric triangle (SYT), ellipse (EPS), second order reciprocal (SOR), and second order exponential (SOE). Both remaining functions are asymmetric and have four parameters - sliding power exponential (SPE) and asymmetric triangle (AST). All six functions achieve reasonable fits of the Kriged grades for the complete profiles. In general, the four-parameter functions yield somewhat lower average absolute errors than do the three-parameter functions. Among the three-parameter functions, considering all profiles, the SOE function yields the best fit, with the SYT function a close second. The EPS function regularly underestimates grade in the halos whereas the SOR function overestimates it. Both four-parameter functions are asymmetric forms of a three parameter function. The better fits for complete profiles of the asymmetric forms do not differ significantly from those for the corresponding symmetric ones. Predictive capabilities for exploration applications are tested by fitting partial profiles, then comparing the resulting distributions with the remaining data of the complete profile. These predictions are of questionable value if all the known data are located prior to the element maximum. However, from the maximum onward, useful predictions of eventual deposit size may be made.

• Research Organization: Harvard Univ., Cambridge, MA (USA)
• OSTI ID: 6462449
• Report Number(s): CONF-8510489-
• Conference Information: Journal Name: Geol. Soc. Am., Abstr. Programs; (United States) Journal Volume: 17
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580100* -- Geology & Hydrology-- (-1989)
ABUNDANCE
AVAILABILITY
CHEMICAL COMPOSITION
COMPARATIVE EVALUATIONS
COPPER ORES
EXPECTATION VALUE
EXPLORATION
FORECASTING
GEOLOGIC MODELS
MAPPING
MATHEMATICAL MODELS
MATHEMATICS
NATURAL OCCURRENCE
ORE COMPOSITION
ORES
PETROCHEMISTRY
STATISTICAL MODELS
STATISTICS